Method for engineered geothermal system in-situ conformance improvement treatment using brines infused with co2

ABSTRACT

A method of repairing a well is provided. The method includes injecting a brine solution into the well, injecting carbon dioxide into the well, and reacting the brine solution in the reservoir rock with the carbon dioxide to form calcite such that calcite precipitates into the desired flow path between a cold well and a hot well to effectively repair short circuits within the EGS reservoir.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to and claims priority under 35 U.S.C. 119from U.S. Provisional Application No. 63/229,402 filed Aug. 4, 2021,entitled “Apparatus and Method for Engineered Geothermal System in-SituConformance Improvement Treatment using Brines Infused with CO2 (In-SituConformance Improvement Treatment (ICIT)),” the entire contents of whichare fully incorporated by reference herein for all purposes.

BACKGROUND OF CERTAIN ASPECTS OF THE DISCLOSURE

At least some known subterranean technologies include drilling at leastone well into the earth to extract minerals, oil, gas, and/or heat fromthe earth for use on the surface. For example, oil and gas extractionfacilities typically include at least one well that has been drilledinto the earth to free and extract the oil and gas from the ground.Additionally, engineered geothermal systems (EGS) typically include twowells drilled into the earth as a pair, one a cold well and the second acomplimentary hot well. A heat transfer fluid is pumped into the coldwell and extracted from the hot well. The heat transfer fluid absorbsheat from the earth and the heat is used to generate power on thesurface. The wells are typically drilled into the earth using surfacedrills and later completed using fracturing techniques that may crack orfracture the rock to create an engineered geothermal reservoir inotherwise unsuitable rock conditions.

However, during the fracking process, the resultant condition of therock may cause unexpected damage to the earth proximate the well andwithin the engineered geothermal reservoir. For example, the cold andhot wells of the EGS are typically located proximate each other andunexcepted fracturing of the rock may cause highly fluid transmissivefissures or short circuits to form between the cold and hot wells. Theshort circuit would cut the path of the heat transfer fluid short,reducing the area of contact between the heat transfer fluid and theearth and reducing the amount of heat the heat transfer fluid can absorbfrom the earth. Accordingly, there is a need for a system that iscapable of plugging undesirable fractures in wells to improve theoverall viability of the wells and the EGS Project.

BRIEF SUMMARY OF SOME ASPECTS OF THE DISCLOSURE

A number of embodiments of a method of repairing a well, a method forpreparing a brine solution, a method for removing heat from rock withina well using a brine solution for EGS, and a method of fracturing a wellare presented in this application. The embodiments described hereininclude a method of repairing a well. The method includes injecting abrine solution into the well, injecting carbon dioxide into the well,and reacting the brine solution with the carbon dioxide to form calcitesuch that calcite precipitates into the well and repairs undesirablefissures or short circuits in the geothermally hot reservoir rock incontact with fluids injected for heat recovery via the cold well.

The embodiments described herein also include a method of preparing abrine solution. The method includes providing a calcium brine solutionincluding calcium chloride and at least one reaction inhibitor. Themethod also includes adjusting a concentration of at least one reactioninhibitor within the calcium brine solution.

The embodiments described herein also include a method of removing heatfrom rock within a well. The method includes drilling at least one wellfor an EGS. The method further includes injecting a brine solution intothe well. The method also includes transferring geothermal heat from therock to the brine solution.

The embodiments described herein also include a method of fracturing awell. The method includes drilling at least one well and super-cooling abrine solution. The method further includes injecting the brine solutioninto the well and transferring heat from the rock to the brine solution.The method also includes thermally contracting and fracturing the rock,creating a more conductive flow path for later injection of brine usedfor heat transfer purposes.

There are other novel aspects and features of this disclosure. They willbecome apparent as this specification proceeds. Accordingly, this briefsummary is provided to introduce a selection of concepts in a simplifiedform that are further described below in the detailed description. Thesummary and the background are not intended to identify key concepts oressential aspects of the disclosed subject matter, nor should they beused to constrict or limit the scope of the claims. For example, thescope of the claims should not be limited based on whether the recitedsubject matter includes any or all aspects noted in the summary and/oraddresses any of the issues noted in the background.

DRAWINGS

The preferred and other embodiments are disclosed in association withthe accompanying drawings in which:

FIG. 1 illustrates a flow diagram of a method of repairing a well inaccordance with aspects of the present disclosure.

FIG. 2 illustrates a flow diagram of a method of preparing a brinesolution in accordance with aspects of the present disclosure.

FIG. 3 illustrates a flow diagram of a method of removing heat from rockwithin a well using an EGS in accordance with aspects of the presentdisclosure.

FIG. 4 illustrates a flow diagram of a method of fracturing a well inaccordance with aspects of the present disclosure.

DETAILED DESCRIPTION

A number of embodiments of a method of repairing a well, a method forpreparing a brine solution, a method for removing heat from rock withina well using a brine solution for EGS, and a method of fracturing a wellare presented in this application. In general, each of the methodsdescribed herein use a brine solution to repair a well, absorb heat froma well, and/or fracture the rock around a well. Specifically, in theillustrated embodiments, the brine solution includes a calcium brinesolution. More specifically, in the illustrated embodiments, the brinesolution includes a calcium rich brine solution. The calcium brinesolution has several unique properties that enable the solution torepair and/or fracture wells and absorb heat from the geothermally hotreservoir rock in contact with brine pumped into a well.

Specifically, in some embodiments, the calcium brine solution may beinjected into the well with liquid carbon dioxide (CO₂) and pH adjustersuch that the calcium brine solution, the liquid carbon dioxide, and thepH adjuster react to precipitate calcite (CaCO₃) in the flow paths wherethe injected brine is flowing through the fractures in the hot reservoiroutside the walls of the cold well casing on its path to the hot well.The calcite precipitates into undesired fissures or short circuits inthe EGS reservoir's flow paths and plugs the undesired fissures or shortcircuits in the well. As such, the calcium brine solution may be used toimprove an inefficient EGS project's heat recovery.

Additionally, in some embodiments, the calcium brine solution may have ahigh heat capacity and may be capable of absorbing large amounts ofheat. As such, the calcium brine solutions described herein may becapable of absorbing greater amounts of heat than current EGS fluidswhile also being capable of repairing fissures and fractures in theadjacent reservoir rock such that the efficiency of an EGS is increasedand the EGS produces more power.

Moreover, in some embodiments, the calcium brine solution may have alower freezing point than fluids typically used to fracture a well.Specifically, in some embodiments, the freezing point of the calciumbrine solution may be close to 0° F. Injecting the calcium brinesolution into the well at 0° F. may rapidly reduce the temperature ofthe well, causing contraction of the rock proximate to the well andcausing the rock to further fracture due to thermal contraction.

Thus, the brine solutions described herein may be used to provide one ormore of the following improvements/advantages over conventionalsystems: 1) simpler and easier in-situ repair of EGS wells, 2) improvedheat transfer for EGS, 3) improved fracturing of rock in contact withEGS wells, and/or 4) increased operating range for EGS and fracturingfluids.

Calcium Brine Solution

The calcium brine solution is typically an aqueous solution includingcalcium chloride. Calcium chloride is an inorganic salt with thechemical formula CaCl₂). It is a white crystalline solid at roomtemperature, and it is highly soluble in water. Typically, the calciumbrine solution includes approximately 5% to 15% by wt. calcium chloride,approximately 15% to 25% by wt. calcium chloride, and/or approximately25% to 38% by wt. calcium chloride.

In some embodiments, the calcium brine solution is a rich calcium brinesolution having an increased amount of calcium chloride, sourced from ageologic reservoir found by exploration and drilling to depths at morethan 100 feet below the surface. For example, in some embodiments, therich calcium brine solution includes approximately 5% to 15% by wt.calcium chloride, approximately 15% to 25% by wt. calcium chloride,and/or approximately 25% to 38% by wt. calcium chloride.

In some embodiments, the calcium brine solution is a supersaturatedcalcium brine solution having an increased amount of calcium chloride.For example, in some embodiments, the supersaturated calcium brinesolution includes approximately 30% to 40% by wt. calcium chloride,according to the historical and current temperature and pressure foundat the geologic source of the brine.

As discussed in greater detail below, the calcium brine solution is usedin the methods described herein to react with other injectants to repaira EGS project's well, fracture a well, and/or transfer heat to/from rockwith a well. More specifically, with respect to repairing a well, thecalcium brine solution is used to react with other injectants to formcalcite precipitate within fissures and short circuits in the adjacentreservoir rock proximate to the brine well in need of repair. As such,in alternative embodiments, the calcium brine solution may include anycalcium containing ionic or covalent compound that enables calcite toprecipitate within fissures and short circuits within the well.

Additionally, as discussed in greater detail below, the calcium brinesolution may be used to absorb heat from rock within the well and, assuch, has a high heat capacity directly related to the Specific Gravity(S.G.) of the calcium brine solution. For example, the calcium brinesolution has a S.G. of approximately 1.04 to approximately 1.13,approximately 1.13 to approximately 1.23, and approximately 1.23 toapproximately 1.40 S.G.

Additionally, as discussed in greater detail below, the calcium brinesolution may be chilled and used to fracture rock within the well byheat fracturing the rock. As such, the calcium brine solutions describedherein have a lower freezing point that typical fracking fluids. Forexample, the freezing point of the calcium brine solution may beapproximately 28° F. to approximately 12° F., approximately 12° F. toapproximately minus 22° F., and approximately minus 22° F. toapproximately minus 35° F.

In alternative embodiments, the brine solutions described herein may beany type of brine solution that enables the brine solutions to operateas described herein. For example, the calcium brine solution may includeany calcium containing ionic or covalent compound that enables calciteto precipitate within fissures and short circuits within the reservoirrock proximate to the EGS well. Additionally, the brine solution mayhave any freezing point and/or heat capacity that enables brine solutionto operate as described herein.

Liquid Carbon Dioxide

As described herein, liquid carbon dioxide (CO₂) is pumped into wellswith the calcium brine solution to react with the calcium brine solutionto precipitate calcite into the fissures and short circuits ingeothermally hot reservoir rock contacted by brine fluids pumped into anEGS reservoir through at least one cold well. In order to pump thecarbon dioxide into well in sufficient quantities to precipitate calciteand plug the fissures and short circuits within the well, the carbondioxide is in liquid form. More specifically, in the illustratedembodiment, the liquid carbon dioxide has a pressure of at least 75pounds per square inch (PSI) and a temperature below 88.0° F. (thecritical point) and above −69.9° F. (the triple point).

In alternative embodiments, the liquid carbon dioxide may have anypressure and temperature that enables the methods described herein tooperate as described herein. Additionally, in alternative embodiments,rather than carbon dioxide, any chemical may be injected into the wellwith the calcium brine solution that enables the precipitation ofcalcite.

pH Adjuster

As discussed in greater detail below, the calcium brine solution is usedin the methods described herein to react with other injectants to repaira well, fracture a well, and/or transfer heat to/from rock with a well.A pH adjuster is used to adjust the pH of the injectants to enable theprecipitation reaction to occur. Specifically, in the illustratedembodiment, the pH adjuster is a base or proton donor that adjusts thepH of the hydrated CO₂ and calcium chloride brine solution to becomemore basic. More specifically, in the illustrated embodiment, the pHadjuster includes ammonium hydroxide (NH₄OH. Ammonium hydroxide adjuststhe pH of the injectants such that the precipitation reaction occursfast enough to precipitate calcite and plug the fissures and shortcircuits within the flowpaths encountered by the treatment fluid beingpumped to repair the EGS project well.

In the illustrated embodiment, the concentration of the ammoniumhydroxide pH adjuster is determined by lab testing conducted as part ofthe planned well repair (ICIT) treatment. Additionally, in theillustrated embodiment, the pH of the injectants after the ammoniumhydroxide pH adjuster has been added is approximately 7.0 toapproximately 9.0.

In alternative embodiments, the pH adjuster may be any solution thatadjusts the pH such that the precipitation reactions described hereinproceed fast enough to precipitate calcite as described herein.

Metals or Other Reaction Inhibitors within the Calcium Brine Solution

In some embodiments, the calcium brine solution may include componentsthat inhibit or retard the precipitation reaction described herein. Forexample, in some embodiments, the calcium brine solution may includecopper (Cu) or zinc (Zn). The copper and/or zinc may inhibit or retardthe precipitation reaction such that the reaction does not occur insufficient precipitation speed or quantities to plug the fissures and/orshort circuits within the well. As such, in order to react theinjectants as described herein, the copper and/or zinc may be removedfrom the calcium brine solution to sufficiently low concentrations topermit the precipitation reaction to occur as designed.

Additionally, the copper and/or zinc may be used to delay, tune, oradjust the precipitation reaction such that the precipitation reactionoccurs at a specific location within the well. For example, if a shortcircuit has been detected within an EGS at a specific location withinthe flow path brine follows as it exits the wellbore perforations in theEGS cold well, a predetermined amount of copper and/or zinc may be addedto the calcium brine solution to inhibit or retard the precipitationreaction until the injectants have reached the short circuit. When theinjectants reach the location of the short circuit within the well, thecopper and/or zinc within the injectant has been reacted or otherwiseused such that the precipitation reaction is allowed to proceed, and theshort circuit is plugged with calcite. As such, the copper and/or zincenables the injectants to target specific regions within the EGSwellbore and brine flow paths for repair.

In the illustrated embodiment, the calcium brine solution may includeapproximately 1 mg/L to approximately 5 mg/L of copper, approximately 5mg/L to approximately 25 mg/L of copper, and/or approximately 25 mg/L toapproximately 250 mg/L of copper. Additionally, the calcium brinesolution may include approximately 1 mg/L to approximately 5 mg/L ofzinc, approximately 5 mg/L to approximately 25 mg/L of zinc, and/orapproximately 25 mg/L to approximately 250 mg/L of zinc. In alternativeembodiments, the calcium brine solution may include any concentration ofcopper and zinc that enables the calcium brine solution to operate asdescribed herein

In alternative embodiments, the calcium brine solution may include anyreaction inhibitor and/or any reaction retarding agent that enables thecalcium brine solution to operate as described herein.

Method of Repairing A Well

FIG. 1 illustrates a flow diagram of a method 100 of repairing a well.As shown in FIG. 1 , the method 100 includes injecting 102 a brinesolution into a well. In the illustrated embodiment, the brine solutionincludes a calcium brine solution as described above. In someembodiments, the brine solution may include a rich brine solution asdescribed above. In some embodiments, the brine solution may include asupersaturated brine solution as described above.

The method 100 may further include injecting 104 carbon dioxide into thewell. In the illustrated embodiment, the carbon dioxide includes aliquid carbon dioxide as described above. In alternative embodiments,the carbon dioxide may include a chemical that includes carbon dioxidethat disassociates from the chemical to react with the brine solution asdescribed herein.

The method 100 may further include reacting 106 the brine solution withthe carbon dioxide to form calcite such that calcite precipitates intothe well and repairs fissures or short circuits within the well.Specifically, as shown in EQNS. 1 and 2 below, the brine solution isreacted with the carbon dioxide to form calcite.

CO₂+H2O↔H₂CO₃  EQN. 1

CaCl₂+H₂CO₃+NH₄OH⁻↔CaCO₃  EQN. 2

As shown in EQNS. 1 and 2, carbon dioxide forms carbonic acid which isreacted with calcium chloride and ammonium hydroxide to form calcite.The calcite precipitates into a solid within the fissure or shortcircuit to plug the fissure or short circuit and re-direct subsequentinjected brine process fluid to hotter areas of the EGS reservoir.

The method 100 may further include injecting 108 a pH adjuster into thewell with the brine solution and the carbon dioxide. In the illustratedembodiment, the pH adjuster includes a basic solution. Specifically, inthe illustrated embodiment, the pH adjuster includes ammonium hydroxideas described above. The pH adjuster is configured to adjust the pH ofthe brine solution and the carbon dioxide such that calcite isprecipitated within the fissure or fracture that contributed to a flowpath short circuit between the cold well and the hot well in EGS. Morespecifically, as described above, the pH adjuster adjusts the pH of theinjectants to approximately 7.0 to approximately 9.0.

The method 100 may further include adjusting 110 a concentration of areaction inhibitor within the brine solution. Specifically, theconcentration of the reaction inhibitor may be reduced or increased to aconcentration that delays the precipitation reaction described herein.Additionally, the concentration of the reaction inhibitor may be reducedto a concentration that permits the precipitation reaction to occuruninhibited described herein. The presence of metal ions in fairly lowconcentrations (typically <500 ppm) can inhibit the carbonate mineralprecipitation process. In EGS well intervention treatments, the metalions may be selectively removed to less than approximately 10 ppm, priorto pumping the brine solution, thereby increasing the speed andefficiency of the calcium carbonate precipitation process. This providesan on-site treatment lever that provides unique control over the levelof flow re-direction from existing flow paths to new or less effectiveflow paths within the EGS reservoir. In this process, the earth's heatcapacity is “mined efficiently” by the brine process fluid using ICITconformance technology as described herein.

The method 100 may further include removing 112 the precipitated calcitein using an acidic solution. More specifically, if the flow pathintervention material, specifically the calcite precipitated in theformation fractures, is to be removed in all or part, an acidizingtreatment may be used. This type of remedial acidizing treatment hasbeen used to remove calcite scale and similar limestone and dolomiteminerals from oil and gas reservoirs. Therefore, the risk of completely“sealing off” a flow path from injector to producer is mitigated andmanageable.

Method 100 includes direct, in-situ flow path intervention placed viaEGS injector (cold) wellbore which alters hydraulic flow and thermalfluid properties at the complimentary EGS producer (hot) wellbore. Aspecified thru-wellbore treatment which uses industrial grade fluidsincluding Calcium Chloride Brine, Liquid Carbon Dioxide, and variouspH-swing process reagents is pumped through the injection well'scompleted zone(s) into the flow paths that are short circuited and notproviding the level of heat transfer required for the EGS project.

During some oil and gas well drilling and completion projects atborehole temperatures under 275° F., the use of a stable brine solutionwith similar physical and chemical properties is an accepted and provenmethod of controlling abnormally high well pressures and mitigating clayswelling and salt zone erosion when drilling and completion fluidscontact certain susceptible formations. Polymer additives are often usedin these situations; however, they have no applicability above 275° F.as they degrade and lose the viscosity-building properties they aredesigned to provide and hence are not applicable for use in EGS drillingand completion projects. This same viscosity degradation is common forall common fracturing (frac) fluids that contain linear gels orcrosslinked gel systems as their base fluids. These gelled fluidstypically have a S. G. of 8.34-9.0 prior to the addition of proppant.This loss of viscosity and proppant carrying capacity can preclude thesegel systems for EGS well completions which are not thermally constrainedby costly wellbore cooldown processes. The only viable EGS multi-stagedeep stimulation alternative is to use essentially a clean water withnear drinking water levels of minerals for the base drilling andfracturing fluid systems. Proppant loads for these clean frac fluidsystems would typically be much lower than one using a brine solutionfor the base fluid because of the ability of this higher S. G. fluid tocarry the additional mass of proppant load without the consequences ofwell bore and/or near wellbore screen-out.

The method 100 improves flow path efficiency in EGS reservoir systemsand the reagents are introduced as a separate, planned and monitored“treatment” aimed to redirect fluid flow in-situ to eliminate or correct“short circuits” in the EGS reservoir that are not allowing efficientheat transfer to occur. Post treatment, certain reagents can be placedvia injection into the wellbore to help ensure that a long-lastingCalcium Carbonate mineralization deposit is retained in the EGSreservoir over the life of the project.

EGS requires the ability to control the flow of fluids through andthroughout the created reservoir. Conventional approaches for alteringflow through a reservoir are borehole centric where flow control into orout of a well is centrally managed from the wellbore. Aspects of thetechnology and techniques set out herein can be used to control flowregimes outside of the wellbore and within the reservoir and to mitigateundesirable flow and heat transfer rates that degrade the performance ofEGS reservoirs.

Method for Preparing A Brine Solution

FIG. 2 illustrates a flow diagram of a method 200 of preparing a brinesolution. As shown in FIG. 2 , the method 200 includes providing 202 abrine solution. In the illustrated embodiment, the brine solutionincludes a calcium brine solution as described above. In someembodiments, the brine solution may include a rich brine solution asdescribed above. In some embodiments, the brine solution may include asupersaturated brine solution as described above.

In the illustrated embodiment, the brine solution may include additionalreaction inhibitors or retarding agents that inhibit or slow theprecipitation reaction. As described above, the reaction inhibitors orretarding agents may include metal ions including copper and zinc. Inorder to enable the precipitation reaction to occur as described herein,the method 200 may further include adjusting 204 a concentration thereaction inhibitors or retarding agents within the brine solution. Morespecifically, in some embodiments, adjusting 204 a concentration thereaction inhibitors or retarding agents within the brine solution mayinclude reducing 206 the concentration of the reaction inhibitors orretarding agents within the brine solution. In alternative embodiments,adjusting 204 a concentration the reaction inhibitors or retardingagents within the brine solution may include increasing 208 theconcentration the reaction inhibitors or retarding agents within thebrine solution.

The method 200 may further include adding 210 a pH adjuster to the brinesolution to adjust a pH of the brine solution. The pH adjuster isconfigured to adjust the pH of the brine solution such that calcite isprecipitated within the fissure or short circuit of the well. Morespecifically, as described above, the pH adjuster adjusts the pH of thebrine solution to approximately 7.0 to approximately 9.0.

The brine solution is a stable, saturated, subsurface-sourced brinesolution that enables the continual EGS process cycling of the brinesolution without loss (or addition through solubility) of minerals tothe reservoir with changes in temperature during the injection,production, and reinjection circular process. The brine solutiontypically has a low pH, such as 1.5-5. This lower pH is mildly acidicthereby reducing the chance of plugging of established and created flowpaths that are desirable for thermal heat recovery.

Method for Removing Heat From Rock Within A Well Using A Brine Solutionfor EGS

The brine solution may be used as the actual process fluid for the heatexchange and continuous reinjection for re-heating process in an EGSsystem, either open-loop or closed loop. The thermal properties of astable, saturated brine solution provides superior mass heat exchangeboth at the surface during conventional binary cycle power generation(steam turbine) and downhole in the heat transfer process where theprocess fluid thermal contact with the hot reservoir rock is critical tothe overall heat exchange and electric power efficiency rating for agiven EGS project. The physical and chemical properties of the brinesolution that is utilized during the drilling, completion, and remedialflow path correction phases of an EGS project are unique and haveimportant value to the overall efficiency and success of an EGS project.The specific gravity of brines which can range from 1.04 S.G. to 2.0S.G. due to TDS or dissolved minerals load is important due to theincreased thermal capacity per unit of volume, and the ability of thebrine to carry additional mass and inertia as it is pumped into awellbore during drilling, completion, and remedial well interventionphases over the life of an EGS project.

FIG. 3 illustrates a flow diagram of a method 300 of removing heat fromrock within a well using an EGS. The method 300 includes drilling 302 atleast one well for the EGS. The method 300 further includes injecting304 a brine solution into the well. In the illustrated embodiment, thebrine solution includes a calcium brine solution as described above. Insome embodiments, the brine solution may include a rich brine solutionas described above. In some embodiments, the brine solution may includea supersaturated brine solution as described above. The method 300 alsoincludes transferring heat 306 from the rock to the brine solution. Themethod 300 may further include flowing 308 the brine solution to asurface facility. The method 300 may also include producing power 310 atthe surface facility using the brine solution. Producing power 310 atthe surface facility using the brine solution may include producingpower using a turbine and the brine solution.

Method of Fracturing a Well

The brine solution may be super-cooled to well below the 32° F. freezepoint of typical water based drilling and fracturing fluid. A calciumbrine solution has a concentration of 38% by wt. calcium chloride andhas a freeze point of approximately minus 35° F. As such, the costs ofheating fracturing fluids on the surface using propane or natural gasfired “hot oilers” are eliminated in Northern Climates during the coldermonths. In Hot Dry Rock (HDR) EGS projects, simply pre-chilling thecalcium chloride brine fracturing fluid and circulating the wellbore to“cool down” the near wellbore region can provide novel means of ensuringthat any number of wireline conveyed electronic instruments that areunreliable at temperatures above 275° F. can function and survive thetrip in and out of the wellbore.

Additionally, the brine solution may be super-cooled and injected intothe well to further fracture the reservoir rock in contact with thesuper-cooled injected fluids injected in the wellbore as part of thecompletion process. More specifically, because the calcium brinesolution has a freezing point below the freezing point of water, thecalcium brine solution may be injected into the well at temperaturesthat are below the lower operating temperatures of most fracturingfluids. The super-cooled brine solution thermally contacts the rockwithin the well, substantially cooling and thermally contracting therock. The thermal contractions cause the rock to fracture rock incontact with the well.

FIG. 4 illustrates a flow diagram of a method 400 of fracturing a well.The method 400 includes drilling 402 at least one well. The method 400also includes super-cooling 404 a brine solution. The method 400 furtherincludes injecting 406 the brine solution into the well. In theillustrated embodiment, the brine solution includes a calcium brinesolution as described above. In some embodiments, the brine solution mayinclude a rich brine solution as described above. In some embodiments,the brine solution may include a supersaturated brine solution asdescribed above. The method 400 also includes transferring heat 408 fromthe rock to the brine solution. The method 400 further includesthermally contracting and fracturing 410 the rock.

A number of embodiments of a method of repairing a well, a method forpreparing a brine solution, a method for removing heat from rock withina well using a brine solution for EGS, and a method of fracturing a wellare presented in this application. In general, each of the methodsdescribed herein use a brine solution to repair a well, absorb heat froma well, and/or fracture the rock around a well. Specifically, in theillustrated embodiments, the brine solution includes a calcium brinesolution. More specifically, in the illustrated embodiments, the brinesolution includes a calcium rich brine solution. The calcium brinesolution has several unique properties that enable the solution torepair and/or fracture wells and absorb heat from the rock within awell.

Specifically, in some embodiments, the calcium brine solution may beinjected into the well with liquid carbon dioxide (CO₂) and pH adjustersuch that the calcium brine solution, the liquid carbon dioxide, and thepH adjuster react to precipitate calcite (CaCO₃) on the walls of thewell. The calcite precipitates into undesired fissures or short circuitsin the well and plugs the undesired fissures or short circuits in thewell. As such, the calcium brine solution may be used to repair wellsand insure that the wells are in compliance with all applicableregulations.

Additionally, in some embodiments, the calcium brine solution may have ahigh heat capacity and may be capable of absorbing large amounts ofheat. As such, the calcium brine solutions described herein may becapable of absorbing greater amounts of heat than current EGS fluidswhile also being capable of repairing fissures and fractures in thereservoir contacted by process fluids injected into the cold well suchthat the efficiency of an EGS is increased and the EGS produces morepower.

Moreover, in some embodiments, the calcium brine solution may have alower freezing point than fluids typically used to fracture a well.Specifically, in some embodiments, the freezing point of the calciumbrine solution may be close to 0° F. Injecting the calcium brinesolution into the well at 0° F. may rapidly reduce the temperature ofthe well, causing contraction of the rock within the well and causingthe rock to further fracture due to the contraction.

Thus, the brine solutions described herein may be used to provide one ormore of the following improvements/advantages over conventionalsystems: 1) simpler and easier in-situ repair of wells, 2) improved heattransfer for EGS, 3) improved fracturing of rock within wells, and/or 4)increased operating range for EGS and fracking fluids.

Terminology and Interpretative Conventions

Any methods described in the claims or specification should not beinterpreted to require the steps to be performed in a specific orderunless stated otherwise. Also, the methods should be interpreted toprovide support to perform the recited steps in any order unless statedotherwise.

Spatial or directional terms, such as “left,” “right,” “front,” “back,”and the like, relate to the subject matter as it is shown in thedrawings. However, it is to be understood that the described subjectmatter may assume various alternative orientations and, accordingly,such terms are not to be considered as limiting.

Articles such as “the,” “a,” and “an” can connote the singular orplural. Also, the word “or” when used without a preceding “either” (orother similar language indicating that “or” is unequivocally meant to beexclusive—e.g., only one of x or y, etc.) shall be interpreted to beinclusive (e.g., “x or y” means one or both x or y).

The term “and/or” shall also be interpreted to be inclusive (e.g., “xand/or y” means one or both x or y). In situations where “and/or” or“or” are used as a conjunction for a group of three or more items, thegroup should be interpreted to include one item alone, all the itemstogether, or any combination or number of the items.

The terms have, having, include, and including should be interpreted tobe synonymous with the terms comprise and comprising. The use of theseterms should also be understood as disclosing and providing support fornarrower alternative embodiments where these terms are replaced by“consisting” or “consisting essentially of.”

Unless otherwise indicated, all numbers or expressions, such as thoseexpressing dimensions, physical characteristics, and the like, used inthe specification (other than the claims) are understood to be modifiedin all instances by the term “approximately.” At the very least, and notas an attempt to limit the application of the doctrine of equivalents tothe claims, each numerical parameter recited in the specification orclaims which is modified by the term “approximately” should be construedin light of the number of recited significant digits and by applyingordinary rounding techniques.

All disclosed ranges are to be understood to encompass and providesupport for claims that recite any and all subranges or any and allindividual values subsumed by each range. For example, a stated range of1 to 10 should be considered to include and provide support for claimsthat recite any and all subranges or individual values that are betweenand/or inclusive of the minimum value of 1 and the maximum value of 10;that is, all subranges beginning with a minimum value of 1 or more andending with a maximum value of 10 or less (e.g., 5.5 to 10, 2.34 to3.56, and so forth) or any values from 1 to 10 (e.g., 3, 5.8, 9.9994,and so forth).

All disclosed numerical values are to be understood as being variablefrom 0-100% in either direction and thus provide support for claims thatrecite such values or any and all ranges or subranges that can be formedby such values. For example, a stated numerical value of 8 should beunderstood to vary from 0 to 16 (100% in either direction) and providesupport for claims that recite the range itself (e.g., 0 to 16), anysubrange within the range (e.g., 2 to 12.5) or any individual valuewithin that range (e.g., 15.2).

The terms recited in the claims should be given their ordinary andcustomary meaning as determined by reference to relevant entries inwidely used general dictionaries and/or relevant technical dictionaries,commonly understood meanings by those in the art, etc., with theunderstanding that the broadest meaning imparted by any one orcombination of these sources should be given to the claim terms (e.g.,two or more relevant dictionary entries should be combined to providethe broadest meaning of the combination of entries, etc.) subject onlyto the following exceptions: (a) if a term is used in a manner that ismore expansive than its ordinary and customary meaning, the term shouldbe given its ordinary and customary meaning plus the additionalexpansive meaning, or (b) if a term has been explicitly defined to havea different meaning by reciting the term followed by the phrase “as usedin this document shall mean” or similar language (e.g., “this termmeans,” “this term is defined as,” “for the purposes of this disclosurethis term shall mean,” etc.). References to specific examples, use of“i.e.,” use of the word “invention,” etc., are not meant to invokeexception (b) or otherwise restrict the scope of the recited claimterms. Other than situations where exception (b) applies, nothingcontained in this document should be considered a disclaimer ordisavowal of claim scope.

The subject matter recited in the claims is not coextensive with andshould not be interpreted to be coextensive with any embodiment,feature, or combination of features described or illustrated in thisdocument. This is true even if only a single embodiment of the featureor combination of features is illustrated and described in thisdocument.

INCORPORATION BY REFERENCE

The entire content of each of the documents listed below areincorporated by reference into this document. If the same term is usedin both this document and one or more of the incorporated documents,then it should be interpreted to have the broadest meaning imparted byany one or combination of these sources unless the term has beenexplicitly defined to have a different meaning in this document. Ifthere is an inconsistency between any of the following documents andthis document, then this document shall govern. The incorporated subjectmatter should not be used to limit or narrow the scope of the explicitlyrecited or depicted subject matter. —U.S. Prov. App. No. 63/229,402,titled “Apparatus and Method for Engineered Geothermal System in-SituConformance Improvement Treatment using Brines Infused with CO2 (In-SituConformance Improvement Treatment (ICIT)),” filed on Aug. 4, 2022.

What is claimed:
 1. A method of repairing a well, the method comprising:injecting a brine solution into the well; injecting carbon dioxide intothe well; and reacting the brine solution with the carbon dioxide toform calcite such that calcite precipitates into the well and repairsfissures or short circuits within the well.
 2. The method of claim 1,further comprising injecting a pH adjuster into the well with the brinesolution and the carbon dioxide.
 3. The method of claim 1, furthercomprising adjusting a concentration of a reaction inhibitor within thebrine solution.
 4. The method of claim 1, further comprising removingthe precipitated calcite in using an acidic solution.
 5. The method ofclaim 1, wherein the brine solution comprises a calcium brine solution.6. The method of claim 1, wherein the brine solution comprises a richcalcium brine solution.
 7. The method of claim 1, wherein the brinesolution comprises a supersaturated calcium brine solution.
 8. A methodof preparing a brine solution, the method comprising: providing acalcium brine solution, the calcium brine solution comprising calciumchloride and at least one reaction inhibitor; and adjusting aconcentration of at least one reaction inhibitor within the calciumbrine solution.
 9. The method of claim 8, wherein adjusting aconcentration of at least one reaction inhibitor within the calciumbrine solution comprises reducing the concentration of at least onereaction inhibitor within the calcium brine solution.
 10. The method ofclaim 8, wherein adjusting a concentration of at least one reactioninhibitor within the calcium brine solution comprises increasing theconcentration of at least one reaction inhibitor within the calciumbrine solution.
 11. The method of claim 8, further comprising adding apH adjuster to the calcium brine solution to adjust a pH of the calciumbrine solution.
 12. A method of removing heat from rock within a well,the method comprising: drilling at least one well for an EngineeredGeothermal System; injecting a brine solution into the well; andtransferring heat from the rock to the brine solution.
 13. The method ofclaim 12, further comprising flowing the brine solution to a surfacefacility.
 14. The method of claim 13, further comprising producing heatat the surface facility using the brine solution in a circular, closedheat exchange system.
 15. The method of claim 14, wherein producingpower at the surface facility using the brine solution comprisesproducing power using a turbine and the heat extracted from the brinesolution.
 16. The method of claim 12, wherein the brine solutioncomprises a calcium brine solution.
 17. A method of fracturing a well,the method comprising: drilling at least one well; super-cooling a brinesolution; injecting the brine solution into the well; transferring heatfrom the rock to the brine solution; and thermally contracting andfracturing the rock.
 18. The method of claim 17, wherein super-cooling abrine solution comprises super-colling the brine solution to atemperature less than 20° F.
 19. The method of claim 17, whereinsuper-cooling a brine solution comprises super-colling the brinesolution to a temperature less than −0° F.
 20. The method of claim 17,wherein super-cooling a brine solution comprises super-colling the brinesolution to a temperature less than −20° F.